Energy
Hadi Farzan; Mohammad Hossein Shahsavari
Articles in Press, Accepted Manuscript, Available Online from 10 February 2024
Abstract
This study analyzes the thermal efficiency of a new perforated cross-flow solar air heater (SAH) integrated with encapsulated phase change material (PCM) by using an experimnetal method. Since SAHs represent low thermal efficiencies, this study introduces a novel SAH that uses two methods to address ...
Read More
This study analyzes the thermal efficiency of a new perforated cross-flow solar air heater (SAH) integrated with encapsulated phase change material (PCM) by using an experimnetal method. Since SAHs represent low thermal efficiencies, this study introduces a novel SAH that uses two methods to address this problem: the perforated absorber with cross-flow configuration and encapsulated latent heat storage (PCM) units. The perforated cross-flow configuration improves the turbulence and, consequently, the heat exchange rate in SAHs and improves instantaneous efficiency. PCM units store thermal energy, prolong the operating period, and increase long-term efficiency. To perform thermal analysis, a perforated SAH with encapsulated PCM units was fabricated and tested outdoors at mair = of 0.012 kg/s and 0.024 kg/s in autumn while ambient and operating parameters were monitored. The experimental data reveal that the outlet temperature reaches the peak value of 38 oC and 32 oC at mair = 0.012 kg/s and 0.024 kg/s, respectively, 12 oC and 6 oC higher than the ambient temperature. During the day, the charge/discharge process occurs in the encapsulated PCM units, avoids sharp temperature gradients and flattens the outlet and absorber temperatures’ profiles. The fabricated SAH reaches the highest thermal efficiency of nearly 83.7% at mair = 0.024 kg/s, which is a suitable value compared to common SAHs.
Energy
Z. Aouissi; F. Chabane; M. S. Teguia
Abstract
The study shows an experimental investigation for a solar air collector with a single pass by adding rectangular baffles for different positions inside the channel. The aim of this study is to improve the thermal efficiency for this collector, and that through testing four cases of baffles positions ...
Read More
The study shows an experimental investigation for a solar air collector with a single pass by adding rectangular baffles for different positions inside the channel. The aim of this study is to improve the thermal efficiency for this collector, and that through testing four cases of baffles positions (mode 1, 2, 3, 4). The study was done under different operating conditions by changing the mass flow rates and positions of baffles. The results show the effectiveness of the baffles in improving the efficiency of the collector, The study also proved that the baffles positions affect thermal efficiency, where the greatest efficiency was recorded in the fourth mode and then in the positioning of obstacles at the middle of the channel for the mode 2 and the mode 4 with a percentage of 76.61 and 90.9, at mass flow rate m=0.0522 kg/s, while the pressure drop was very high in the mode 4, and after that the mode 2. Through the conditions of the study and taking into account all the results; we can say that the best case was mode 2.
Energy
H. Farzan; A. A. Abouee-Mehrizi; M. Khazali
Abstract
The current study introduces and analyzes a novel square cross-flow perforated solar air heater (SAH). Since the convection mechanism in SAHs is weak, numerous methods have been suggested to address this problem and improve thermal efficiency. Perforations and cross-flow configuration generate high turbulency ...
Read More
The current study introduces and analyzes a novel square cross-flow perforated solar air heater (SAH). Since the convection mechanism in SAHs is weak, numerous methods have been suggested to address this problem and improve thermal efficiency. Perforations and cross-flow configuration generate high turbulency and, consequently, high convection rate resulted. Hence these methods have been applied to enhance thermal efficiency. To achieve this goal, an experimental setup was fabricated and tested at outdoor conditions for two air mass flow rates (mair) of 0.015 kg/s and 0.03 kg/s while several sensors monitored the collector’s heat dynamics and ambient conditions. The obtained results illustrate that outlet temperature reaches the peak values of 38 oC and 34 oC, which is only 6 oC and 7 oC lower than the maximum absorber temperature. This crucial issue proves a high heat exchange rate in the fabricated SAH that causes the absorber temperature to approach the outlet temperature due to high turbulency. The strong convection mechanism in the fabricated SAH improves daily thermal efficiency, in which its value reaches nearly 78.6% for the mass flow rate of 0.03 kg/s. In conclusion, the square cross-flow perforated SAH is an economy, applicable, compact collector, ensuring high thermal efficiency.
Energy
H. Farzan; M. Mahmoudi; E. Hasan Zaim
Abstract
Solar air heaters (SAHs) have an inherent drawback: the conventional mechanism is low inside these collectors’ types. Use of perforations is a simple technique to improve convection, and this investigation experimentally assesses a novel design SAH utilizing three inclined perforated absorber plates. ...
Read More
Solar air heaters (SAHs) have an inherent drawback: the conventional mechanism is low inside these collectors’ types. Use of perforations is a simple technique to improve convection, and this investigation experimentally assesses a novel design SAH utilizing three inclined perforated absorber plates. Two scenarios are considered to assess the dynamics and efficiency of this perforated SAH, including mair = 0.012 kg/s and 0.024 kg/s. Numerous sensors monitored the dynamics of the perforated SAH and ambient factors for 12 hours in October 2022. The experimental outcomes illustrate that the perforation method remarkably enhances the thermal efficiency of the perforated SAH compared with standard smooth SAHs. The daily thermal efficiency of the perforated SAH reaches 73.30% and 82.65%, while the outlet air temperature experiences peak values of 39 oC and 42 oC at noon and keeps within 90% of its maximum value for 2 hours for the scenarios considered. Improving the convection mechanism causes the flowing air to extract the absorber’s thermal energy more effectively. Hence the SAH can produce an airstream near its maximum temperature for an extended duration. In conclusion, the perforation method is a robust, simple method to boost the thermal efficiency of SAHs.
Energy
H. Bagheri Sabzevar; Z. Erfan
Abstract
Today’s energy consumption is one of the most important causes of pollution around the world. Considering the building sector consumes the most energy, it should be seriously considered. In order to provide thermal comfort inside a building, energy is consumed, which can be managed using tools ...
Read More
Today’s energy consumption is one of the most important causes of pollution around the world. Considering the building sector consumes the most energy, it should be seriously considered. In order to provide thermal comfort inside a building, energy is consumed, which can be managed using tools such as louvers that allow solar radiation to pass through the windows while reducing the amount of consumed energy. The goal of this paper is to find the optimal features for shading device of fixed louvers for the east, west, and south facades of the office building at Hakim Sabzevari University in terms of thermal efficiency using parametric analysis. For one year, three rooms on three floors of this building with window louvers at different depths, angles, and distances were thermally simulated with EnergyPlus software and the HoneyBee plugin in addition to the Galapagos plugin for optimization. Based on the optimized samples, it is possible to reduce the thermal energy consumption by 32.34%, 23.71%, and 30.2%, respectively using the ideal louvers on the east, south, and west facades. In terms of thermal efficiency, the distance between the blinds on the south facade and the angle between them on the east and west facades of a window louver are the most significant factors.
S. Talesh Amiri; R. Shafaghat; O. Jahanian; A. H. Fakhari
Abstract
To better homogenize the mixture of fuel and air in the combustion chamber and to enhance the controllability of ignition timing in Reactivity Controlled Compression Ignition (RCCI) engines, controlling the start of injection (SOI) timing can be essential. By changing the SOI timing, at some specific ...
Read More
To better homogenize the mixture of fuel and air in the combustion chamber and to enhance the controllability of ignition timing in Reactivity Controlled Compression Ignition (RCCI) engines, controlling the start of injection (SOI) timing can be essential. By changing the SOI timing, at some specific crank angles (CAs), the fuel can impact the edge of the piston bowl and create some difficulties. In this research, initially, efforts are made to recognize the range of SOI timing in which this collision process takes place (in the range of 44-54° bTDC), then, performance and the emission levels of the engine were evaluated in the beginning and end of this interval. The findings suggest that the nitrogen oxides emissions and the maximum in-cylinder mean pressure are higher in SOI of 44° bTDC, as compared to those in the SOI timing of 54°bTDC, although the latter has higher ignition delay and unburnt hydrocarbon (UHC) emission. Moreover, some evaluations were carried out to examine how the temperature of the fuel-air mixture can affect the performance of the engine in this specific range. It was found that as the IVC temperature increases, it rises the indicated mean effective pressure (IMEP), in-cylinder pressure, and NOx emission.
S. W. Igo; N. Kokou; A. Compaoré; P. Kalifa; G. L. Sawadogo; D. Namoano
Abstract
This work is devoted to the evaluation of the performance of a typical fired-wood oven commonly used in the rotisserie sector in Burkina Faso. The methodology used is based on the energy balance of the oven. For this purpose, 20 liters of water were heated up to 90 °C. The difference in water temperature ...
Read More
This work is devoted to the evaluation of the performance of a typical fired-wood oven commonly used in the rotisserie sector in Burkina Faso. The methodology used is based on the energy balance of the oven. For this purpose, 20 liters of water were heated up to 90 °C. The difference in water temperature at the start and at the end of the experiment makes it possible to calculate the amount of energy consumed by the load. The temperatures of the walls as well as that of the ambient were recorded to evaluate the losses by convection towards the environment. The losses through the fumes have been estimated from the energy balance. The results show that the dominant losses are those of fumes (about 55 % of the energy consumed). The losses through the walls are relatively large (26 %). The efficiency of the oven is around 19 %, which is very low. These results show that these equipment are inefficient and contribute significantly to the waste of wood at the national level.
S. Rai; P. Chand; S. P. Sharma
Abstract
This paper represented theoretically investigation of energy and exergy performance of an offset finned solar air heater. Parametric study was done to investigate the effect of variation of offset fin parameters i.e. fins spacing (1 to 5cm) and fins height (1.8 to 5.8cm) at different mass flow rates ...
Read More
This paper represented theoretically investigation of energy and exergy performance of an offset finned solar air heater. Parametric study was done to investigate the effect of variation of offset fin parameters i.e. fins spacing (1 to 5cm) and fins height (1.8 to 5.8cm) at different mass flow rates (0.01388 to 0.0833kg/s) on the energy and exergy efficiency. The results indicated that attaching offset finned below the absorber plate at low mass flow rates can lead to noticeable enhancement of exergy efficiency. The results revealed that the trend of variation of the energy and exergy efficiencies are not the same and the exergy efficiency is the chief criterion for performance evaluation. Decreasing the fins height, reducing the fins spacing are effective at low mass flow rates, but at high mass flow rates the inverse trend is observable, such that exergy efficiency reduces sharply. The efficiencies of offset finned solar collector were compared with conventional flat-plate collectors and longitudinal fins collector.
H. B. Kulkarni
Abstract
A Cylindrical parabolic trough (CPT) collector of aperture width 1.03 m and length of 1.82m was designed and fabricated. CPT was covered with glass of thickness of 3 mm to avoid convective heat loss. Reflector coated with polished aluminum sheet having reflectivity 0.87 and receiver tube made of mild ...
Read More
A Cylindrical parabolic trough (CPT) collector of aperture width 1.03 m and length of 1.82m was designed and fabricated. CPT was covered with glass of thickness of 3 mm to avoid convective heat loss. Reflector coated with polished aluminum sheet having reflectivity 0.87 and receiver tube made of mild steelcoated with black zinc having absorptivity of 0.94 were used for CPT. mass flow rate of working fluid was 4 l/h. Thermal performance of CPT collector was tested according to ASHRAE Standardmethods. Average instantaneous efficiency of closed cylindrical parabolic trough collector system was found to be 66%. The overall efficiency of CPT system is 71% which is best suited for solar thermal applications.
